Thermostatic electric switch.



' F. KUHN.

THERMOSTATIG ELEGTRXG SWITCH.

APPLICATION FILED APR.18, 191s.

lSDQSO Patented Mar. 9, 1915 FRANKEUHN, or DETROIT. MICHIGAN.

THEBMOSTATIC ELECTRIC SWITCH.

Specification of Letters Patent.

Patented Mar. 9, 1915.

Application iled April 18, 1913. Serial N0. 762,157.

To all 'whom 'it may concern.'

Be it known that I, FRANK KUHN, a citizen of the United States of America, residing at Detroit, in the county of Wayne and State of Michigan, have invented certain new and useful Improvements in Thermostatic 'Electric Switches, of which the following is a specification, reference being had Atherein to the accompanying drawings.

The invention relates to thermostatic electrical switches, and consists in the novel construction as hereinafter set forth.

In the drawin s: Figure l is a perspective view of a switch; Fig. 2 is a longitudinal section therethrough; and Fig. 3 is `a cross.

section. y

A is a section of metallic tuoing, and `B is a metallic bar formedof aamaterial having a different coelicient of expansion and of 'a slightly bowed form, as shown. The bar B is arranged inside of the tube A, and is secured to one of-the sides thereof by screws or other fastening devices C at opposite ends. To facilitate the attachment of the member B the tube A is cut away upon the opposite side at D so as to provide suitable insulator material.

, tain temperature is an` opening for the insertion of a screwdriver or other engaging tool.

Upon the outer face ofthe tube and opposite the bar B` is secured a contact member E, which is insulated from the tube by an interposed insulation F of mica or other The .contact member E is secured .in this position by screws G, which pass through insulator bushings H in the member into 4engagement with a threaded aperture in the` memr A. An insulator washer I interposed between the head of the screw Gand the member E completes the insulation.

J is a contact screw whichl is secured to the-member E and passes through an aperture in the tube A into roximity or into contact with the .member E In operation, one of the terminals of the electric circuit is attached to the tube A and the other to the contact memberlil' This will normally close the circuit by the passage of current through the contactserew J s the free end of which is in contact With the bowed bar B. As soon, however, as a cerreached, the differential expansion of the bar B and tube .A will cause the former to separate sllghtly from the contact screw J, so that the circuit is member to said tube,

- metallic tubel of open., Upon the cooling of the parts, the

screw and curved bar will again come intov contact, which will close the circuit.

Where the bar B having a comparatively low fusing point, it 1s des1rable toprovide a contact thereonof dliierent material, such as shown atKK. This contact coperates with the contact screw J in the manner above described.y

What I claim as my invention is:

1. Ay thermostatic switch, comprising a metallic tube, a bowed member formed of metal having avdiiferent co-eiiicient of expanslon than said tube and arranged within the same, means for securing said bowed an insulation mounted upon one face of the tube, a metallic strip mounted upon said insulation, insulated securing means connecting said metallic strip and lnsulation to said tube, and a contact member mountedv upon said Vmetallic strip,

insulated from said tube and the latter into operative bowed member. v

2. A thermostatic switch, comprising a metallic tube, a bowed member formed of a metal having adifferent coeiiicient of expansion arrangedv within said tube and secure to one of the sidesthereof at its opposite ends, a contact member mounted upon and insulated from said tube on the side opposite said bowed member, means for securing said contact member to said tube and a contact screw engaging said outer contact member and passing through an aperture in said tube into operative relationvwith said bowed member.

3. A vthermostatic switch, comprising a vmetallic tube of rectangular'cross section, a bowed bar formed of a metal having'a different coefficient of expansion arranged within said tube and secured-at its opposite ends to projecting into relation to the one of the sides of said tube," a contact mem- 4. A thermostatic switch, comprising a l rectangular cross section, a bowed bar formed of metal having a differ; ent'coeiiicient -of expansion arranged within said tube and secined at 'itsopposite endsto one' of thesides of the tube, the opposite sidfe of said tube opposite the ends of said bowed in presence o two witnesses.

bar being cut away, a contact member adjacent to the outer face 'of the side of the tube to which s aid bowed meinber is secured,

sgidcontact member being Insulated there# `Vif'itnesses member ana'maing within sabria tube inw operative relaton with said bowed bar. 10

In testimon whereof I aix my signature FRANK-KUHN.

` JAMES P. BARRY, HENRI E. BowMAN. 

